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Saturday, 24 April 2010

The Client Access Server Role Pt1

The Client Access Server Role

Exchange Server 2010 now handles all client connections via the CAS role includingconnections made by Outlook MAPI clients. This connection type was previously handled by the mailbox server role. The CAS role now has the RPC Client Access Service which allows communication with AD and then the mailbox server. Having Outlook clients connect to the CAS role provides a significant improvement in terms of mailbox server failover.
Clients can connect to Exchange CAS using a number of different technologies which include:

Web based email (Outlook Web Access or OWA)

Mobile devices

Outlook Anywhere

Outlook Web Access

OWA is enabled by default and ready to go on CAS machines without any more configuration. However there are some changes you can make to optimize your experience.OWA and External URLs

You should ensure that the CAS machine has an external URL assigned. This might have been configured during Exchange installation. The external URL should be the public DNS name that clients use to connect to the Exchange organization from the Internet. The external URL is used for redirecting connecting clients to a CAS server in the same site as the users mailbox. Here's how it works:

Bob provides a url in his browser, https://london.compulinxtraining.com/owa

The London CAS server queries AD and determines from the GC that the mailbox for Bob is located in Paris.

This external URL is then given back to Bob, https://paris.compulinxtraining.com/owa

If Paris CAS does not have an external URL assigned, then the London CAS proxies the connection to the Paris CAS. Bob will stay connected to London and the London CAS will connect to Paris CAS on Bobs behalf.

To set the external URL for the CAS server, I highly recommend that you perform the action in the Exchange console:

Open the Exchange Management Console and browse to the Server Configuration > Client Access Node

Enter the external DNS name and add the name of the CAS server that will be connected to use the name defined.

Click the configure button to set the external URLs on the CAS machines. The Exchange control panel URL should also be automatically configured to use the same URL as defined here.

Select the Exchange Control Panel Tab

Select the ECP virtual directory and choose properties from the action menu

Define the URL as the same value as above but make sure you use the virtual directory of /ecp instead of the /owa

The above method provides you with a single process to define the external URL and in my humble opinion should be used. However, the shell equivalent involves defining the external URL on a number of different virtual directories. Here's how: